A new class of carbon materials with useful properties has been produced by chlorination of metal carbides. When reacting with metal carbides, such as silicon carbide SiC or titanium carbide TiC, chlorine forms stable volatile compounds with metals but does not react with carbon at high temperatures. The remaining carbon rearranges itself into a structure, as a pure surface film, which is a derivative of the original ceramic compound. Using this technology, carbon coatings with low friction coefficients and high hardness have been produced from bulk SiC and TiC. In previously reported methods, the production of the low-friction carbon films involves high-temperature chlorination, such as between 1073–1273 K, of the carbide. The carbon coatings have low friction coefficients and high hardness produced from bulk SiC and TiC using high-temperature chlorination of the carbide. There are practical difficulties encountered when protecting silicon from attack by chloride radicals used in various processes. Hence, silicon has to be protected with a mask. Standard masking materials are unable to withstand the high temperatures and significantly long times used for the high-T chlorination process.
The production of a thin layer of low-friction carbon at a specific location of a device that is susceptible to high wear and damage due to frequent sliding contact would be highly desirable. Moving microelectromechanical systems (MEMS) devices are ideal candidates for the application of such coatings as MEMS are known to degrade due to wear and friction on contacting surfaces. Titanium carbide has been one of the preferred coatings for improving the performance of macroscopic moving mechanical components due to the inherent established wear resistance. These TiC coatings have been applied to critical interfaces of a MEMS micromotor and directly integrated into the device fabrication scheme. However, in addition to being able to deposit TiC at sliding interfaces, the proper lubrication of TiC versus a second TiC interface is very important. The conversion of a thin layer, between 50 nm and 1000 nm, of TiC to low-friction carbon may substantially improve the performance of a moving MEMS device by providing both wear-resistant and low-friction interfaces.
The previously reported processes for the production of the low-friction carbon films from SiC, involves high-temperature chlorination of SiC, on the order of 1000° C., in a 3.5% Cl2 chlorine with Ar-96.5% gas. However, critical problems exist when applying this process to the fabrication of micro devices. Such devices are typically produced on a silicon substrate, which itself is susceptible to attack by Cl or F radicals and must be protected from the halogenation process. Standard photolithographic mask materials are not capable of withstanding the high temperatures employed in the chlorination process. For these reasons, an alternative low-temperature process for the generation of low-friction carbon films from hard carbides is highly desirable. These and other disadvantages are solved or reduced using the invention.